Searching for the Lowest-Mass Supermassive Black Holes with Chandra
Abstract
Relations between supermassive black holes (SMBHs) and their host galaxies are now well known, but several questions remain: Do all galaxies harbor SMBHs? Do correlations between BH mass and host galaxy properties extend to lower mass BHs and all galaxy types? Is the galactic bulge or the dark matter halo the defining component for the nuclear BH? Answering these questions requires a study of low mass SMBHs, in particular those that reside in the latest-type spiral galaxies. While the presence of an active galactic nucleus (AGN) provides almost certain proof of the existence of an SMBH, galaxies that are not known to host AGNs may nevertheless have SMBHs at their centers. Thus a galaxy may appear quiescent when in reality there is an accreting SMBH, if the accretion level is low enough. We present a search for such SMBHs by looking for evidence of low-level nuclear activity, using the Chandra X-ray Observatory, in a well-defined sample of nearby quiescent spiral galaxies. The survey includes new snapshot observations of 37 galaxies, which are combined with archival data for a further 18 galaxies. We use multi-wavelength data where available to help distinguish AGNs from other types of x-ray sources. The detections and nondetections provide constraints on the accretion luminosity and therefore the growth rates of SMBHs in the local universe, and also address the question of the prevalence of SMBHs in spiral galaxies that do not have bulges. Only 2 out of 14 galaxies of type Sd are detected.
This work was supported by the National Aeronautics and Space Administration through Chandra Award No. GO7-8111X issued by the Chandra X-ray Observatory Center.- Publication:
-
American Astronomical Society Meeting Abstracts #213
- Pub Date:
- January 2009
- Bibcode:
- 2009AAS...21331601G